Light control device



Jul 18, 1939. K. GR OMUS 2,166,491

. LIGHT CONTROL DEVICE Filed Aug. 19, 1937 l tdi'llidz' Karl 6mm:

Patented July 18, 1939 UNITED STATES PATENT OFFICE Application August 19, 1937, Serial No. 159,982 In Austria August 26, 1936 2 Claims.

Checking of the optical sound record which is necessary in the production of talking films or picture sound films, is as a rule eifected in the following manner: The light rays used for the sound records pass through a slot diaphragm controlled by the oscillations of the microphone current and influence a photo-electric cell, converting the variations of light intensity again into electric energy which is led to an amplifier and from there to an earphone or loudspeaker. This method of checking the sound record is, however, uncertain because the energy converting device itself contains sources of errors.

According to the present invention, the reliability of checking is increased by the fact that the movable part of the light controlling member is connected with a membrane, directly or indirectly, in such a manner as to cause the latter to perform audible vibrations. The operations of the microphone, sound amplifier and light controlling device are thus able to be acoustically checked without additional apparatus. The volume of the sound waves radiating from the membrane of the light controlling device is a reliable check for the correct regulation of the sound reception apparatus. Supervision of the optical sound recording device then requires only ascertaining whether the sound recording film moves without trouble. I

A constructional form of a device according to the present invention is shown by way of example in the accompanying drawing of which Fig. 1 is a central section; Fig. 2 is a plan view, whilst Fig. 3 is a side elevation showing the movable part of the slot diaphragm seen from the left side of Fig. l.

The light controlling device may in a known manner comprise a movable part I and a stationary part 2 between which parts a slot or gap 3 is left, through which pass the collected rays of a source of light (not shown in the drawing). The movable part I of the slot diaphragm, which in the constructional form shown in the drawing has the shape of half a hollow cylinder (see Fig. 3), carries at its lower end an oscillating coil 4 through which the microphone current flows. The oscillating coil 4 is arranged in the field of a pot magnet 5 provided with an exciting winding 6. The magnet 5 is accommodated in a housing I to the upper flange of which a bridge member 8 is secured, holding in a vertical guide the stationary part 2 of the slot diaphragm, which part may be adjusted vertically so as to obtain the most favorable average width of the slot or gap 3.

The movable part I of the slot diaphragm is connected with a membrane I 0, the rim of which membrane is secured to the upper flange of the housing 1.

The fluctuations of the microphone current flowing through the oscillating coil 4 cause the said oscillating coil to move up and down within the magnetic field in accordance with these fluctuations. On the one hand, by the movement of the coil the slot or gap 3 gets smaller or larger according to the fluctuations, and, on the other hand, the membrane connected with part 2 is brought to oscillate; since the oscillations produced thereby correspond to the fluctuations of the microphone current, they reproduce the sound such as it has been received by the microphone sothat checking is possible.

The connection of the membrane with the movable part I of the slot diaphragm presents the further advantage that the said part is centrally guided by said membrane and that the oscillations of said part are damped.

As a matter of course, the movable part of any diaphragm otherwise constructed may be connected with a membrane in a similar way. Generally speaking, the light controlling apparatus may be modified in various manners over the constructional form as described above.

What I claim is:

l. A light controlling device for the production of sound films comprising a magnet, an oscillating coil disposed in front of the said magnet and being influenced by the microphone currents transmitting the sound to be recorded, a light controlling device connected with the said oscillating coil and a loud-speaker membrane connected with the said oscillating coil, said membrane being so arranged and constructed as to make the oscillations of the said coil directly audible to the operator for enabling him to check the function of the sound recording apparatus, and an additional slidable adjusting member arranged in juxtaposition to the light controlling device.

2. A light controlling device for the production of sound films comprising a magnet, an oscillating coil disposed in front of the said magnet and being influenced by the microphone currents transmitting the sound to be recorded, a light controlling device connected with the said oscillating coil and a cone-type loud-speaker membrane connected with the said oscillating coil concentrically with respect to said light controlling device, said membrane being so arranged and constructed as to make the oscillations of the said coil directly audible to the operator for enabling him to check the function of the sound recording apparatus, and an additional slidable adjusting member arranged in juxtaposition to the light controlling device.

KARL GROMUS. 

